UTD’s Technical Diver program is a progressive process. If already previously certified by other agencies, usually the first class is Essentials of Technical Diving, with or without Nitrox. After completing Essentials of Technical Diving, or achieving an equivalent skillset through other UTD classes, you can move on to Techreational Diver, 130'/39m with Oxygen decompression or move straight into the Technical Diver 1 course.
The Technical Diver 1 course moves you to 160'/48m using Nitrox 50% or Oxygen for decompression. Optionally, divers may train to use a stage bottle to make it easier to conduct multiple technical dives in the same day.
This is followed by the Technical Diver 2 course which goes to 200'/60m with two decompression bottles.
These are building block classes which gradually introduce you to deeper depths and staged decompression in a slow progression by first focusing on bottom skills, then ascent skills and finally mid-water skills.